Bathymetric modeling of sediments and organic carbon of polluted rivers in southeastern China     

Yubao Li  Di Wu  Ronald W. Thring  Donna Delparte  Jianbing Li 《Journal of Soils and Sediments》2016,16(9):2296-2305

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Investigation of lichens using molecular techniques and associated mineral accumulations on a basaltic flow in a Mediterranean environment     

Joselito M. Arocena  Tariq Siddique  Ronald W. Thring  Selim Kapur 《CATENA》2007,70(3):356-365

The role of lichens in the breakdown of rocks in various environments is well documented. We investigated the formation of secondary minerals under 13 different fungal species growing on a basaltic flow in Sanliurfa (Turkey) to understand the influence of lichen species on the transformation of minerals in a Mediterranean environment. We used molecular technique (rDNA sequence) to identify 13 different species of lichens (7 crustose, 5 foliose and 1 pathogenic). X-ray diffraction and scanning electron microscopy were used to determine the composition of mineral accumulations. The formation of quartz and 2:1 phyllosilicates in various layers (top, brown and white) of the weathered basaltic flows under all the lichen colonies may be the result of precipitated silica alone (quartz) or in combination with aluminum (2:1 clays) released as a by-product during the breakdown/weathering of primary silicate minerals present in the basalt. However, aeolian deposition may also be a possible source of these mineral species. Whewellite, a calcium oxalate mineral, accumulates in the weathered basalt underneath all the species of lichens. We believe that the formation of whewellite was due to organic acids excreted by fungal hyphae to dissolve primary minerals (e.g., olivine and feldspars); this lichen-mediated process released enough calcium and generated oxalate necessary for the formation of whewellite.  相似文献   

Immobilization of Heavy Metals by Co-pyrolysis of Contaminated Soil with Woody Biomass     

F. Debela  R. W. Thring  J. M. Arocena 《Water, air, and soil pollution》2012,223(3):1161-1170

We investigated the potential application of pyrolysis treatment to a mixture of woody biomass and a metal-contaminated soil as an alternative eco-friendly option to stabilize metals in soils. Our specific objective was to test the optimum combination of high heating temperature (HHT) and heating time to effectively encapsulate metals in a contaminated soil into a biochar. For this purpose, we used a laboratory bench batch reactor to react a mixture of multi-element metal contaminated soil with 0% (control) 5%, 10%, and 15% (w/w) sawdust. Each mixture was reacted at 200°C and 400°C HHT for 1 and 2 h heating times. Physicochemical and morphological characterization along with standard EPA Synthetic Precipitation Leaching Procedure (SPLP) test were conducted to assess the effectiveness of the heat treatment to immobilize the metals in the contaminated soil. Compared to controls, we recorded up to 93% reduction in Cd and Zn leachability after 1 h heat treatment at 400°C, with the addition of 5–10% biomass. Pb leaching was reduced by 43% by the same treatment but without the addition of biomass. At lower pyrolysis temperature (200°C), however, there was a substantial increase in both As and Zn leaching compared to the untreated controls. Our study suggests that several factors such as the type of metal, heating temperature, heating period, and the addition of biomass influence the efficiency of pyrolysis to immobilize metals in the contaminated soil.  相似文献   

Biochar amendment of chromium-polluted paddy soil suppresses greenhouse gas emissions and decreases chromium uptake by rice grain     

Zhou  Jiangmin  Chen  Hualin  Tao  Yueliang  Thring  Ronald W.  Mao  Jianliang 《Journal of Soils and Sediments》2019,19(4):1756-1766

Purpose

Soil chromium (Cr) pollution has received substantial attention owing to related food chain health risks and possible promotion of greenhouse gas (GHG) emissions. The aim of the present study was to develop a promising remediation technology to alleviate Cr bioavailability and decrease GHG emissions in Cr-polluted paddy soil.

Materials and methods

We investigated the potential role of biochar amendment in decreasing soil CO₂, CH₄, and N₂O emissions, as well in reducing Cr uptake by rice grains at application rates of 0 t ha^?1 (CK), 20 t ha^?1 (BC20), and 40 t ha^?1 (BC40) in Cr-polluted paddy soil in southeastern China. In addition, the soil aggregate size distribution, soil organic carbon (SOC) concentration of soil aggregates, soil available Cr concentration, and rice yield were analyzed after harvesting.

Results and discussion

Biochar amendment significantly reduced CO₂, CH₄, and N₂O emission fluxes. Compared to CK, total C emissions in the BC20 and BC40 treatments decreased by 9.94% and 17.13% for CO₂-C, by 30.46% and 37.10% for CH₄-C, and by 34.24% and 37.49% for N₂O-N, respectively. Biochar amendment increased the proportion of both the 2000–200 μm and 200–20 μm size fractions in the soil aggregate distribution. Accordingly, the organic carbon concentration of these fractions increased, which increased the total SOC. Moreover, biochar amendment significantly decreased soil available Cr concentration and total Cr content of the rice grains by 33.6% and 14.81% in BC20 and 48.1% and 33.33% in BC40, respectively. Rice yield did not differ significantly between biochar amendment treatment and that of CK.

Conclusions

Biochar application reduced GHG emissions in paddy soil, which was attributed to its comprehensive effect on the soil properties, soil microbial community, and soil aggregates, as well as on the mobility of Cr. Overall, the present study demonstrates that biochar has a great potential to enhance soil carbon sequestration while reducing Cr accumulation in rice grains from Cr-polluted rice paddies.

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